Reflector.



No. 835,648. PATENTED NOV. 13, 1906.

R. STRAUBEL.

REFLECTOR.

APPLIUATION FILED MAR. 13, 1906.

2 SHEETS-SHEET 1.

PATENTED NOV. 13, 1906.

R. VSTRAUBEL.

REFLECTOR.

APPLICATION FILED MAR.13, 1906.

2 SHEETS-SHEET 2.

Zia?

,. UNITED STATES ATENT-omen.

RUDOLF STRAUBEL, or JENA, "GERMANY, Assrcsoa .TO THE FIR'M' or j CARL ZEISS, or JENA, GERMANY.

REFLECTOR...

' A Specification or Letters Patent.

Patented Nov. 13, 1906.

- Amilima'oumoa Kai-oh 184m. sermxasoaau.

To'aZZ whom may con loamy "7 Be it known that I, RUDOL'F STRAU'BEL, doctor of philosophy, a citizen of the Germ Em' ire, residing 'at Carl-Zeissstrasse, Jena,

in t 6 Grand Duchy of Saxe-Weimar, Germany, have invented a new and useful" Reflec'tor, of which the following is a specifica- "tion.-

f p The invention consists in the im rovement I O of a reflector. system described by eck in the 1887 .volume' of the Zeitschmft Inatrwm'qintenku'nde, pp. 385-9; and designated by ,him

,Tripelspiegel',"(triple reflector.) The object of the invent onis to lessen the'loss of rays peculiar to reflector and to amplify its sco e of actionwithoilt modification of the re ectforf system proper. The triple reflector consists .ofthree plane-mirrors placed in s'uch mutual relation one to another that 'the.three lines of intersection of the reflectingplanes are not parallel, but intersect each other in one pointthe center of the reflector.

I A special form of the triple reflector named center of the reflector is designated as the by Beck Zentralspiegel (central reflector) est. serve to elucidate the invention.

will b In this special form not only the efie cts of the subj cot-matter of the invention resolve themselves into the simplest, but also the triple reflector has in this .form and in those approximating to it its greatest importance.

The reflecting+surfaces of the central reflector are all three at right angles to each other. It forms, consequently, when made of cont' ous s uare mirrors, the half of a hollow cu e. The 'agonal of the cube drawn through the axis. of the reflector. The property to which the central reflector owes its name consists in that on one side the object and on the other side .the reflected image of it (more correctly, the six reflected images of it being coincident) have a situation which is symmetrical about the center which impinges uponone of three refiectin surfaces with any one inclination to the axis of the reflector and in any orientation to the reflector leaves the reflector in a parallel but of the reflector. From this it follows that in general each ente ray.

I times'the case when theray comes to be reflected from all succession. I g V 5 While Beck dealt with the. applicability of 'the central reflector for the determm ation of certain errors of measurement in astronomy,

'Grubb has recently, in theEnglish specifica- 6o tionlNo. 21 ,856/03, called attention'to the fact that the central reflectorpresents other important 'ossi bilitie's when it isused to reflect light 0 a dist ant source toward the place or in theproximity of the source of light, some of these new applications abundant use is made ofthat one property of the. central reflector according to which theangle which the axis of the reflector forms with the direction of entrance of the ra s of light can-vary from zero to one of consi erable size-thirtyfive degrees and more, according to the orientation bf the reflector to the direction, of entrance'without the light failing to return toward its source. the rays deviateirom the direction parallel to the aims of the reflector the image produced loses in intensit because a part of the rays no longer meet t surface, and in certain orientations and wit a large inclination to the axis of the reflector a slighter part does not even meet the second reflecting-surface. This loss ,is therefore the maximum when. the direction of entrance of the-rays has reached the limiting anglethirty-five degrees or more-of the return of the rays, as determined by the orientation for the time being of the reflector. To lessen such loss-that is, to acquireimore rays than formerlyand at the same time to 0 widenthe limiting an les-that isto say, to create threturnof t e rays a ra e of angle hitherto unavailableis the .twofo d aim of the means now proposed. This means, which forms the subject-mattenof the invention, consists in filling up the hol low space of the reflector .Witha transparent body which is opticallymore dense than the air hitherto in contact, with the reflectingsurfaces. plane or approximately plane entrance, and; exit surface which is appropriately laced at right angles to the axis of there ector. Thus originates, when the added optical medium'is a solid bodyfor instance, glassa tetrahedral prism, which itself can be the carthree reflecting-sm'facesin 55 Accordingto the degre 75 e third successive reflecting;

The filling is to-be limited by a zoo flui' ean be advantageously used as filhn F a bode thing ass .rays by this rier of the reflecting-film, so thet the hitherto reflecting-bodies are dispensed with. If the film also be dispensed with, so that total refiection occurs-at the, lass surfaces limited by air, the range of angle of; the returnof the means is of course decreased; but yet, nevertheless, this range of angle can he obtained greater than in the central reflector of former construction, becanse the efliciency of the filling increases as the refractive power of increasesand because ve highEly refractive kinds of glass are rocura 1e. or

g. There thus eubstitutedTfor the glass-prism knowri as the fluid prism, having I walls. It is also possible, however, to use the free fluid surface es the plane entrance and exit surface -of the filling by directing the aperture ef the reflector upward.- A lane-mirror arr'an ed in an-inclined position over-the centra reflector then throwsthe rays which ordinarily come from the distant source of lightin an approximateiy horizontal direction toward the central reflector.

- In the annexed drawings ellh'gures are per- .specti-ve views ofthe same Kin sents a central refiector'and its ima e.

Figure 1 representea central reflector. Fig.- 2 represents a tetrahedron. Fig. 3 re';re 1 4 to 8; are diagrams illustrating t e loss dt light culiar to the central reflector and the tetra edron. Figs. 9 and 10 represent tetrahedra, the acute .solid angles of which are truncated. g

In the central reflector. hitherto-1 con-' structed, as represented in "Fi 1, three lano-paraiiel p ates-carry the, re ecting-suraces, which when complemented-i b three other surfaces (indicated by dotte dines) would form a cube. The diagonal A of-the cube proceeding from the center of'the reflector is the axis of the reflector. L

If the tetrahedral glass prism be constmcted, within a Bike cube, as shown in Fig.

'2,'its. entrance and exit surface orfaperture 1s an equiieteraltriangle a c.

The central reflector shown in Fighas:

the, same equilateral trian ar aperture. 0, 'b c as the tetrahedron in h ig. .bfit represented as arallelto the plane of drawingls. The dotted lines represent the image of t e reflector projected by the reflector itself. The symmetricai position of the aperture 1 b c onthe-one side and of the image a, b c" of the aperture on the other about the center "Gis easily-recognized. It will be'alse seen a b c, together-with its reflected image A is that the portion of the axis A oif-the reflector from the centcrC-to the plane or: the aperture inserted.

The aperture a b c in Fig. 4, with its image.

a. b c as well as the axis-A, with its im e A have heen transferred: from, Fig. 3A.

large central reflectors piencil of parallel rays enterinto the central e ector arallel to the axis A and comletely fil theaperture a b c, it must take the V cm of a triangular prism the edges of which lie, as .i'ndicatedby the arrow-feathers, at the points a, b, and c. As previously alludedto, the position of the emerging rays appertaining to the entering edge re s and directed parallel to them is given by t e center of the reflector lying midway between any two correlated rays. The directions of the reflected edge rays pass, consequently, through the reflected images a, b", and c of. the points a, b, and c. In the figure the imaginary reflected prismatic pencil between the image of the aperture e N c and the plane of a erture is indicated by fine dotted lines. .is evident, the edge rays 0/ a b b ',.and c. c iand partial encils triangular in section neighboring t em out the lane of aperture outside the a erture a b c. means that they shoul receive the third reflection from parts of the reflector which have no real existencethat they fall out from the'pencili reflected back again. The edges of the real reflected pencil are indicated byarrow heads. The cross-section of this pencil is a regular hexagon.

Fig. 5 e111 differsfrom the foregoing by the pencil a mitted through the aperture a c,-ferming an angle with the axis A. The six arrowheads in this case indicate the limits of a realreflected pencil, the cross-section of which isan irregular hexagon and smaller than the pencil parallel te the axis, as in Fig.

4, because with inclined incidence stillmore:

that in F' 3 the space between the three mirrors an the. plane oi apertureisfilled by a prism .of glass of ordinary power of refraction-for 'mstance, of a refractive index 1.5the layerof glass limited by the plane age G of.

sprface ef aperture projects an un the center of the reflector on the axis A, which image is onIy- E sc far removed from this surface as thepoint C itself. From the. same reason the imegea' bc of the aperture will be produced at two-thirds of the -.former distance from the lane ot a erture sequent upon the closerproximity between then erture and its imeafe the trace 03 I1 9"" o the 1m ary r ected prism of raysm the lane 0 a erture has another- Siilllflm tion re ative to t e aperture a b. c than the trace e 11 0 in F' 5. A considerable.por=

tion of the ra s hit ertolost have-been ren= dered: availab e.

With Fig. 7 the description returns once more to the central reflector not filled with glass. This fi ure represents one of the cases where tl i'e prism of rays admitted throu h the a erture a b 0 forms an angle with tie axis 15, which for the iven orientation of the central reflector fa ls a little beyond the limiting angle of the return of the rays. The cross-section of the real reflected rism of rays had already become zero with a l GSSGI' an 1e of orientation.

The infl invention in the case of Fig. 7 is manifested in Fig. 8. The arrow-heads show what crosssection the real reflected prism of rays has which owes its existence'to the employment of a glass tetrahedron.

In Fig. 9 the glass tetrahedron, according to Fig. 2, is again represented. The a erture of Fig. 2 isreduced, however,-by p ane sections parallel to the axis A. to a hexagon. As a com arison with Fig. 4 shows, such a hexagonal opening when regular has the property of reflecting a pencil, filling the aperture and directed parallel to the axis A without loss of rays. At the same time also with incidence of a pencil fillin the aperture and inclined to the axis A the oss of ra s is relatively triflin The same may be said of the aperture wit circular boundary according to Fi 10, where the acute solid angles of the tetra edron are'cut ofl b a coaxial cylindrical surface. Finall t e same holds for every limitation of t e a erture which lies symmetrical about the polnt appertaining to the axis of the reflector of the plane of aperture.

uence of the subject-matter of the What I claim as my invention, and desire to secure by Letters atent, is-

1. A triple reflector being approximately 0 a central reflector and ha its hollow space filled up by an optical me ium, the refractive ower of which exceeds that of air and whic presents to the luminous rays an approximately lane entrance and exit surface perpendicu ar to the axis of the reflector.

2. A tetrahedron made of glass and polished on its four surfaces, three of which constitute approximately a central reflector and the fourth of which is perpendicular to the axis of the said reflector.

3. A triple reflector being approximately a central reflector and consisting of a tetrahedral lass body, the plane entrance and exit s ace of which is er endicular to the axis of the reflector and is limited by a figure symmetrical about the point common to the said surface and to the axis of the reflector.

4. A triple reflector being approximately a central reflector and consisti of a glass tetrahedron, the entrance and exit surface of which is perpendicular to the axis of the reflector and the three acute solid angles of which are cut off each by a plane section par allel to the axis of the reflector, so that the said surface is limited by .a regular hexagon.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

RUDOLF STRAUBEL.

Witnesses:

PAUL KRfiGEL; FRITZ SANDER: 

